1. Field of the Invention
The present invention relates to a semiconductor device with a dielectric capacitor configuration configured by sandwiching a dielectric film between a lower electrode and an upper electrode and a fabricating method thereof, which is applied suitably, in particular, to a ferro-electric memory whose dielectric capacitor configuration has a dielectric film consisting of a material containing a ferro-electric substance.
2. Description of the Related Art
Conventionally, a flash memory and a ferro-electric random access memory (FeRAM) are known as a nonvolatile memory from which stored information does not disappear when the power is interrupted.
The flash memory has a floating gate mounted in a gate insulating film of an insulated gate field-effect transistor (IGFET), and stores information by accumulating charges representing information to be stored in the floating gate. In order to write or eliminate information, it is necessary to flow tunneling current that passes through the insulating film. Thus, a comparatively high voltage is required.
The FeRAM stores information by utilizing hysteresis characteristics of a ferro-electric substance. A ferro-electric capacitor configuration with a ferro-electric film as a dielectric substance between a pair of electrodes generates polarization in response to applied voltages between the electrodes, and has spontaneous polarization when the applied voltage is removed. When polarity of the applying voltage is reversed, polarity of the spontaneous polarization is also reversed. By detecting the spontaneous polarization, information can be read out. The FeRAM has such advantages that it is operated with a low voltage compared with a flash memory and makes a high-speed write-in possible while saving electric power consumption. A system on chip (SOC), in which a FeRAM is adopted to conventional logic technique, is examined for applications such as an IC card.
Refer to Japanese Patent Application Laid-open Nos. 2002-57297, 2002-246564 and 2001-210807.
Upon fabricating a FeRAM, in order to restore damage of a ferro-electric film generated when an upper electrode layer is formed on the ferro-electric film, or when the upper electrode is patterned by processing the upper electrode layer, it is necessary to apply heat treatment (annealing treatment) after the upper electrode is patterned. However, the annealing treatment sometimes causes generation of surface roughness on the upper electrode. Caused by the surface roughness as the primary reason, there are such problems as instability of contact of the upper electrode and generation of short circuit between the upper electrodes to lower process yield.